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The rate of cooling of a body can be expressed as
where
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Chapter 28 Solutions
EBK NUMERICAL METHODS FOR ENGINEERS
- The drag on an airplane wing in flight is known to be a function of the density of air (), the viscosity of air(), the free-stream velocity (U), a characteristic dimension of the wing (s), and the shear stress on the surface of the wing (s). Show that the dimensionless drag, sU2, can be expressed as a function of the Reynolds number, Us.arrow_forwardThe rate of heat flow per unit length q/L through a hollow cylinder of inside radius ri and outside radius ro is q/L=(AkT)/(rori) where A=2/(rori)/ln(ro/ri). Determine the percent error in the rate of heat flow if the arithmetic mean area (ro+ri) is used instead of the logarithmic mean area A for ratios of outside-to-inside diameters (Do/Dj) of 1.5, 2.0, and 3.0. Plot the results.arrow_forwardMatch the laws accordingly. 1.1st law of thermodynamics 2.2nd law of thermodynamics (foward engine) 3.Joules law 4.2nd law of thermodynamics (reverse engine) 5.3rd law of thermodynamics 6.second law of thermodynamics (Carnot) A. The internal energy of a perfect gas is a function of the absolute temperature only B. No Heat Engine can be more efficient than a Reversible Heat Engine operating between the same temperature limits C. A pure crystalline substance at absolute zero temperature is in perfect order, and its entropy is zero D. When a system undergoes a complete cycle, the net Heat supplied plus the net Work input is zero. E. It is impossible for a heat engine to produce a net work output in a complete cycle if it exchanges heat only with a single energy reservoir. F. It is impossible to construct a device that operating in a cycle will produce no effect other than the transfer of heat from a cooler to a hotter body.arrow_forward
- According to the Newton's cooling law, the temperature of any substance is directly related to the distinction between the substance temperature and its environment (ambient) temperature dT =-k(T – T,)k(T-T) dt where Tis the substance temperature (C) T is the time (minute) k is constant T. is environmental temperature A casting ladle of molten metal has 290 °C, By using Euler methodology, evaluate the temperature from t=0 to 35 min with a step size of 2 min. If, T, is 25°C and k is 0,009/min.arrow_forwardA closed thermodynamic system consists of a fixed amount of substance (i.e. mass) in which no substance can flow across the boundary, but energy can. For a closed themodynamic system we cannot add energy to the system, via substance (E ) (1.e. matter which contains energy is not allowed across the boundary) Across the Boundaries E° = No Q = = Yes W mass NO CLOSED = Yes SY STEM m = constant | energy YES Figure 1.1. If the substance inside the thermodynamic system shown in figure 1.1. (i.e. piston cylinder device) is air, is the system a Fixed closed system Moveable closed system A. В.arrow_forwardConsider an introductory thermodynamics class experiment used to demonstrate phase change phenomena. A beaker of water is heated, and its temperature measured over time to establish the temperature at which boiling occurs. The results, shown in the Figure below, are for three separate tests conducted on different days by different student groups using the same equipment and method. Why might the data from three seemingly identical tests show different results? Temperature (°C) 101 100 99 98 97 96 95 94 1 2 3 4 Time (min) 5 Boiling region 100.3 100.1 99.8 Boiling point results Test 1 (762 mm Hg) Test 2 (754 mm Hg) Test 3 (767 mm Hg) 6 7arrow_forward
- re | https://eagleonline.hccs.edu/courses/156500/quizzes/969413/take Question 39 5 pts Perform the following temperature unit conversions: (a) Convert a temperature of 52°C to 'F °R, and K. (b) Convert a temperature of -40°F to °C, K, and °R. Relevant formulae are given below T (°C) = T (K) - 273.15 T ('F) = T (°R) - 459.67 T(F) = 1.8T (°C) + 32 Upload Choose a File 5 pts tion 40arrow_forwardThe process variable of a system which varies with respect to time is called dynamic. True or Falsearrow_forward25 Question 10 Anwer 2 g of air in a piston cylinder is compressed isothermally. The initial temperature is 399 K, the initial pressure is 7.1 bar, and the final volume is 2.8 litres. What is the heat transfer during the process? Give your answer in Joules to the nearest whole number. Far air co1.005 kJ/kgK and cy- 0.718 kJ/kgK.arrow_forward
- Jes 1:01 i docs.google.com/forms what is the Physicists recognize four fundamental forces.* Flectrical force O - Gravitational force -Strong nuclear force Weak nuclear force O -Muscular force Force of friction Ff is described by • Ff = µN * O p synovlal fluld in the Joints P -coefficient of fraction between two surface in The temperature of the human body is normally about 98.6°F.calculate the temperature of the body "C* oC = (5/9)x(oF-32) =5/9(98.6- 32)-37 oc oc=(9/5)x(of -32) =9/5(98,6-32) =13,3 Under resting conditions the body energy is being used as follows * O 27% by the liver and splee O 20-%by the skeletal musules Under resting conditions the body energy is being used as follows. O 19% by the brain. 15% by the kidney. We can write the first law of thermodynamics as: * O AU-AQ -A.. O AU-AQ +AW. 1kcal = J O 1 Kcal =4184j. O O O Oarrow_forwardQ8): To find how much heat is required to bring a kettle of water to its boiling point, you are asked to calculate the specific heat of water at 61°C. The specific heat of water is given as a function of time in Table below. Temperature, T Specific heat, C₂ (°C) J kg-°C 22 42 52 82 100 4181 4179 4186 4199 4217 Determine the value of the specific heat at 7=61°C using the direct T method of interpolation and a third order polynomial. Find the absolute relative approximate error for the third order polynomial approximation (Lagrange Method).arrow_forward3. A metallic rod 20 cm long is heated to a uniform temperature of 100° C. At t = 0 the ends of the bar are plunged into an ice bath at 0° C and thereafter maintained at this temperature. Find an expression for the temperature u(x, t) if the bar is made of cast iron. Material a (cm²/s) Silver 1.71 Copper 1.14 Aluminum 0.86 Cast iron 0.12 Granite 0.011 Brick 0.0038 Water 0.00144 Table 1: Thermal Diffusivity Constants for Common Materialsarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
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